In order to maintain the competitive ability of the 3rd generation mobile communication system in the communication field, the 3rd Generation Partnership Project (3GPP) standard workgroup has been focusing on the research on the Evolved Packet System (EPS). FIG. 1 is an architecture diagram of an EPS according to related art. As shown in FIG. 1, the EPS system mainly comprises the two parts: an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and an Evolved Packet Core (EPC). The EPC of this system can support a user to access via a GSM EDGE radio access network (GERAN) and a Universal Terrestrial Radio Access Network (UTRAN).
The EPC mainly comprises a Home Subscriber Server (HSS), a Mobility Management Entity (MME), a Serving Gateway (S-GW), a Packet Data Network Gateway (PDN Gateway, P-GW), a Serving GPRS Support Node (SGSN) and a Policy and Charging Rules Function Entity.
As shown in FIG. 1, the UTRAN/GERAN and the SGSN are connected to each other via an Iu interface, the SGSN and the HSS are connected to each other via a Gr interface, the MATE and the HSS are connected to each other via an S6a interface, the MME and the SGSN are connected to each other via an S3 interface, the E-UTRAN and the S-GW are connected to each other via an S1-U interface, the S-GW and the P-GW are connected to each other via an S5 interface, the S-GW and the SGSN are connected to each other via an S4 interface, the P-GW and the packet data network are connected to each other via an SGi interface, the E-UTRAN and the MME are connected to each other via an S1-MME interface, the P-GW and the Policy and Charging Rules Function Entity are connected to each other via a Gx interface, the packet data network and the Policy and Charging Rules Function Entity are connected to each other via a Rx+interface.
In particular, the HSS is the permanent storage point of the user subscribed data and is located in the home network subscribed by the user; the MME is the storage point of the user subscribed data in the current network and responsible for a signaling management of the Non-Access Stratum (NAS) from a terminal to the network, tracking and paging management function and bearer management in a user idle mode; the S-GW is the gateway from the core network to the radio system and responsible for the user plane bearer from the radio access network to the core network, data buffering in a terminal idle mode to initiate a service request, legal monitoring, packet data routing and forwarding function; the P-GW is the gateway of the EPS and the external network of this network and responsible for the functions such as charging function, packet filtering, policy application and IP address allocation of the terminal; the SGSN is the service support point for the GERAN and UTRAN user accessing the EPC network, similar to the MME in function, and responsible for the functions such as paging management and bearer management and location updating of the user.
When a change occurs to the coverage region located by a UE, for instance, when traveling from one kind of Radio Access Technology (RAT) coverage region to another kind of RAT coverage region, the UE finds that it enters an unregistered region through monitoring a broadcast channel. In order to ensure the continuity of the service between the UE and the core network, it is necessary to register under the new RAT coverage region, therefore, the UE initiates an inter RAT Tracking Area Update (TAU) or a Routing Area Update (RAU) process.
For a dual-mode UE at the overlapped area or the neighboring region of the UTRAN/GERAN coverage region and the E-UTRAN coverage region, the UE frequently initiates the TAU or RAU process in the two registering region, due to the reasons such as frequently shifting between the two coverage regions or the signal intensity in the overlap area, and it will result in a heavy load of the air interface. Therefore, in the EPS system, the ISR function was introduced to reduce the air interface signaling between the UE and the core network. After this function is activated, the UE which has both the UTRAN/GERAN and the E-UTRAN access function at the same time may register to the MME and the SGSN at the same time, however, the UE registering to the MME and the SGSN via the two access networks respectively are independent. Thus in the above situations, the UE with the activated ISR will not frequently initiate the TAU or RAU process at the neighboring area or the overlapped area of two coverage, thereby, the unnecessary air interface signaling is reduced to save the air interface resource.
In order to ensure the ISR functions properly, the context information of the UE in both the two mobility management units (the MME and the SGSN) need to be kept, and the S-GW is required to save the bearer information of the UE under the two different access technologies. However, when the ISR function can not be kept (i.e., the ISR function is deactivated) due to the reasons such as powering off the UE, detaching from the network, and changing the S-GW, the core network needs a mechanism to ensure that the useless UE context information and the bearer information are released, and to synchronize the ISR states of the UE and the core network side mobility management unit, so as to prevent the information resource from being wasted and avoid the error resulted from the asynchronism of the ISR states.
As to different ISR deactivation scenarios, the prior art employs different treatment modes which are described below.
Scenario 1, when the UE travels to the MME/SGSN which is/are not the two mobility management units with the activated ISR, the TAU/RAU process is needed to be initiated, at this time, the MME/SGSN can only acquire the context information from one of the previously registered mobility management units, it is possible that a activation is needed because the registered context information of the SGSN/MME when ISR function is previously activated cannot be obtained properly which result in that the ISR function can not be kept and is required to deactivated. At this time, one mobility management unit, in which the UE was located previously and whose ISR function is activated, initiates a request for updating or deleting bearer to trigger the S-GW to actively initiate the deleting bearer request to the other mobility management unit with the ISR function being activated.
Scenario 2, when the UE powers off and detaches from the network, the ISR function also needs to be deactivated. In this situation, the mobility management unit in which the UE is located and the ISR function is activated may initiate the deleting bearer request to the S-GW, and may send a detachment instruction to the other mobility management unit associated with the ISR function activation, at this time, the other mobility management unit associated with the ISR function activation is responsible for initiating the deleting bearer request to the S-GW. By this process, both of the two mobility management units associated with the ISR function have deleted the context information of the UE and the bearer information of the S-GW.
Scenario 3, when the network initiates a detachment process which is merely a detachment of an access technology, at this time, the UE may also attach to another access technology. The ISR function also needs to be deactivated in this scenario. But when the S-GW receives a deleting bearer request from a mobility management unit with an ISR function being activated, the deleting bearer request shall not be sent to the other mobility management unit associated with the ISR function activation.
It can be seen from the operation modes of the ISR deactivation of the above first two scenarios, that the behaviors that the S-GW performs towards the deleting bearer request from the mobility management units with the ISR function being activated can not be the same. If Scenario 1 is satisfied, i.e., the S-GW will send the deleting bearer request to the other mobility management unit associated with the ISR activation upon receiving the deleting bearer request from one party; then in Scenario 2, there will be deleting bearer requests in both the direction from the other mobility management unit associated with the ISR function activation to the S-GW and the direction from the S-GW to this mobility management unit, the deleting bearer requests is not only conflict with each other but also redundant.
But in Scenario 3, there is no solution of the ISR deactivation. If the operation mode of Scenario 1 is used, an error operation will occur because the S-GW need not delete the bearer to the other mobility management unit associated with the ISR function deactivation. However, if the S-GW does not send the deleting bearer signaling to the mobility management unit, it can not obtain the information of the current deactivated ISR, at this time, the asynchronsim of the ISR deactivation states will bring into a subsequent flow error; if the operation mode of Scenario 2 is used, the other mobility management unit associated with the ISR function activation will acquire the state information of the ISR deactivation, but the detachment will also occur to the UE, which is an error operation.
Therefore, there is a need for a technology which can avoid the error operation of the ISR function deactivation under the above scenarios.